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Why
do we plan to convert to a Combo Electric/Diesel boat?
This
is the question that will spark the biggest debate about our choices in
setting up S/V Lynx. We know, because the debate about hybrids vs
diesels is heated on the various boat
forums out there, with the majority of the debaters calling for diesel
boats, not electric hybrids. But what if you could have both in a
combo system? Read on.
Going Green
People have asked us if we plan
to go with a
diesel/electric hybrid system because we want a ‘green’ boat? The answer is, ‘no’. It’s
not that we don’t want to save our planet,
we just have other more selfish reasons for our choice in propulsion. We want the comforts that we get from an
electric propulsion system, but also want the security of the power of
the diesels.
On the electric side, we get many
advantages, such as less noise and diesel fumes when running off of the
electric propulsion system. The boat will
carry more battery power which is also useful for air conditioning at
night (without a
generator running). There will be fewer
trips to a fuel dock and far less times carting jerry cans of fuel in a
dinghy. We will also have an endless
supply of electricity
to replace fuel and propane while we are in remote areas.
However,
even though ‘going green’ is not our main reason for adding electric
propulsion to our boat, if
in
the pursuit of our comforts, we also
help put less CO2 into the air, we’ll take it. How
much? Well, that’s open to
debate.
Making solar panels and Lithium
batteries require energy and
that generally adds CO2 into the atmosphere. How
much? Well, there have been
studies done on this. I found one such
study
on the making of solar panels that tells us it will take the first two
years of
service just to make back the energy that was used to make the panel. However, if the panel lasts for 10 years (or
more) then those other eight years are making carbon-free energy,
helping
reduce CO2 output. So, they will make us,
somewhat, green.
But what about those Lithium
batteries? Again, a study was done on a 30
kWh car
battery that showed it would take three and a half years of a
gas-guzzling
vehicle, or more than 50,000 kilometers before the lithium car would
start
beating the gas car on carbon-dioxide emissions. Still,
eventually, it does save CO2.
This means adding an electric pod
motor system will make
us a bit more green than
not doing so. We’ll take it.
But remember, we are not doing this to go green, yet we take it
if it helps. According to these two
studies,
it will.
One final note on a 'Green' boat. Some folks
want to go
completely 'green' by not having a diesel generator or (in our case)
that and diesel motors. In other
words, they don't want to burn a drop of diesel, ever. We would
love to do that! However, our calculations show it just isn't
feasible or safe, at this time. To make it feasible we would need
far more energy dense batteries, something along the lines of ten
times, or more and you would need more solar (which is unlikely since
we are already using all the available space).
65%
use of a 38.4 kWh bank is about 25 kWh of the usable power without
stressing the cells. That amount of power will motor us
for about 3 hours at 5 knots. 5 kWh of solar gives us 25 kWh back
a day,
which takes us about 3 more hours motoring. That's fine for a
trip that only requires that much motoring.
However, on a long passage, you run into a problem. Your 5 kWh
solar array can only recharge 25 kWh a day. Even if your
batteries can hold 250 kWh, it would take ten days of sitting to
recharge them and they would currently weigh 10,000 lbs!
So, unless solar panels magically become far more productive (they
won't, gains are in small percentages) and batteries become ten times
more dense, you still have a problem. Now, if batteries became 60
times more dense, your range would be around 900 miles... that would be
close
to the range of most diesel boats. However, don't hold your
breath on getting 60 times more dense batteries any time soon!
Alternatively,
if batteries became 20 times more dense, and you increased your bank to
three times larger, you could about match a diesel boat's range, then
recharge at port (or by sitting on anchor for a month!).
This is slightly more feasible. You would eliminate the weight of
the
diesel motors and replace it with the weight of the additional
batteries. However, without
significantly increasing the output of solar panels (which isn't
happening), getting a battery
that is 20 times more energy dense than current lithium batteries is
pretty useless. Thus, you still need a diesel generator for range
and diesel engines for enough thrust (for emergencies) to make a
hybrid a safe blue water boat.
Conclusion, we aren't getting rid of diesel fuel anytime soon.
Now, as to the question of safety. The issue is, a reasonably
powerful electric propulsion system that would equal 110 hp (twin 55 hp
diesel motors, in our case) would require far too large a battery bank
to power very large electric motors. 15 kw motors, like the
Oceanvolt system, are really only going to add about 30 hp of
power. You would need to go with four of these to have enough
power. Therefore, you would need 77 kWh of battery storage.
That 77 kw battery bank (which would have to be full at the moment of
the
emergency) would only power you for one hour at full thrust in all four
motors. For longer than
that, you would need two 30 kw diesel generators! Those are
pretty large and expensive. All total, you are looking at a
system that would cost something like $160,000 and weigh quite a
bit, there would be over 1,200 lbs in just the batteries! It's
much cheaper and more efficient (in terms of burning
diesel in an emergency situation) to just have the 55 hp diesel
motors. However, if we just have those, then we lose all the
benefits of an electric propulsion boat, and there are many advantages!
So, the best way for us to get all the comforts and fuel savings an
electric boat offers, yet still have the power and range of diesel
engines for emergencies,
we plan to go with a combo system of the twin 55 hp diesel
engines plus two 7.5
kw electric pods with around 38,400 kWh of batteries.
The
negatives
for going Hybrid over sticking with just Diesel
1) The first negative: the High Cost to convert
a
diesel boat to a Hybrid
Well, that's an issue because it is really expensive. Four
Oceanvolt ServoProps cost an insane $100,000. You need $2,000
worth of
solar panels,
about $13,000 worth of Lithium batteries (77 kw), $20,000 for a
20 kw generator, and there are a few other costs as well. Call it
$130,000, minimum and with all the small extra things you need, it
would top $140,000 installed.
This is a reason why we recently came up with Plan A, which was going
with just two SD15
motors for $36,000. That would also reduce battery size by half
to 38,400 kWh ($6,500). This would reduce the total cost a bit to
$70,000. The problem is that we would be underpowered during an
emergency, though fine for normal uses.
However, now we have come up with Plan B, which saves us nearly
$46,000, making the price to add the pod system $30,000. Read on.
OK, still too expensive? Not so fast. Perhaps it is
better to say,
a large initial outlay of money. As we have shown above, you
will save fuel over time. How much? That entirely depends
on your passages, how many, how far, and the cost of fuel. On our
142,000 nautical mile, meandering, double
circumnavigations of the world, done over fifteen years, calculating
every
projected
passage
(which we have done, see 'Route'), we calculate that (at current
average diesel prices, and assuming they don't go up), we save about
$50,000
in fuel costs (it varies depending on where you buy fuel, this is a
current
average). We also save in other
types of maintenance as well, due to using the generators or engines
less hours. In addition, we save in propane, since we will
convert everything to electric devices. For Plan A, that's about
$37,000
over the sixteen
years. For Plan B, we save about $15,000 (more on why this is
less, later). In total, for upgrading to the hybrid
system, between
fuel and maintenance savings we save $87,000 with Plan A for a net gain
of $17,000. That's not bad. Or, even better, we achieve a
net savings of $47,000 if we go
with Plan B! Now we are talking! Note, this is assuming
the price of diesel does not go
up... if it
does, then we save even more money on either plan. This is
very likely over the 16 years, fuel prices are bound to go up.
Also,
don't forget that new technology always starts out expensive and then,
typically,
it goes down every couple of years and gets better at
the same
time. The cost to convert to a hybrid should drop over
time. If the past is any indication of
technology and price, not too far into the future, the cost will be the
same as diesels, and eventually become even cheaper.
In two more years, when we buy our system, prices might be even
better. Regardless, even at today's prices, we think going Hybrid
with Plan A
or B is worth the initial
outlay of cost if you factor in the rising cost of diesel.
However, at $30,000 outlay, Plan B is a much lower risk in case we are
wrong about the
amount of savings.
2) The Second negative: the Plan A Hybrid would have
Less power
We
are calculating everything for Plan A off
of two 15 kw
electric motors. The manufacturer claims these are near 40 hp
diesels (but captains who installed them report they are closer to 30
hp). If you need more
power you must go with
larger electric motors or move up to four of these. We don't want
to do either of those choices due to the correspondingly larger battery
bank, not to mention the high initial cost. Nor would we have
enough solar panels to charge them back
up in a day or two.
An example of this is that one of the boats we are interested in comes
with 40 hp diesels, but had the option to upgrade to 55 hp
diesels. Most
people opted to upgrade because they felt that 40 hp was
underpowered for that yacht. Therefore, if went with two 15 kw
Oceanvolt motors, using 48 vdc, equivalent to 30 hp, our total hp would
be 60 instead of 110, making the boat severely underpowered. Most
of the time, this
isn't going to matter much since you rarely motor at full
throttle.
However, when you are caught in a bad situation more power is
sometimes needed. Fighting a strong current come to mind, as does
fighting off a lee shore during a heavy blow. However, remember
this, the same boat that has a 55 hp
would do better if they had 75 hp motors. You can always play the
more horsepower is better game.
Still, a minimum horsepower for a given boat to achieve enough thrust
to travel at a sustained 9 knots is desirable and two 15 kw electric
motors will not supply that kind of power.
However, for comparison sake, in the route examples below we will
explore both Plan A and B against a pure diesel engine boat.
The Two Hybrid
Options (Plan A and B):
Plan A: Two Oceanvolt SD 15 kw motors and a 20 kw generator:
In this case, the boat's propulsion system
would consist of two SD15 motors using a Gori three blade
folding
propellers and a 38,400 kWh battery bank backed up by two generators,
one 20 kw and one 10 kw.
We don't need the servo prop models for our boat. The fact
is, we aren't buying a performance
catamaran. If we were, things would be different. We might
have less room for solar panels and the boat would average higher
speeds. Therefore, regeneration would be much more
efficient and desirable. But for our boat, that won't be true as
our average speed will be more like 7 knots instead of 10.
Example, an SD15 ServoProp generates 1 kw at about 8 knots, but 2 kw at
10 knots. With our boat, we won't be going much more than 8 knots
all that often, and 6 or 7 knots a lot of the time. Therefore,
regeneration isn't that advantageous. Add in the fact that
regeneration slows the boat down by at least half a knot per motor, so
you would only want to use it when the boat is sailing at fast
speeds. On a production boat, like we plan to use, you will find
that you won't
want to use regeneration all that often. And, on the days where
the wind is blowing strongly enough for good regeneration, we won't
need
the energy to motor anyway, since there is plenty of wind to sail.
So, based on this, it works out better to buy two SD15
motors (the non-servo prop model) using Gori folding props. This
would
cut down on
the electric motor's computer aided complexity and cost less if we
happened to hit something with a brass
prop vs. computer controlled blades. Not to
mention, the SD15s are cheaper than the ServoProps by $7,000 per
motor.
Plan B:
Stick with the existing diesels and add two 7.5 kw pod motors:
So,
more data came through from
two of the boats using Oceanvolt motors, and they listed a couple of
issues. One boat was struck by lightning and lost all propulsive
power since they were a purely electric propulsion boat. The
other boat
quit their
circumnavigation because they were not generating enough power through
regeneration.
Let's start with that second boat. They only had 2 kw of
solar
panels
and no generator. Those were both mistakes, in our opinion.
Based on the numbers we ran, you need about 5 kw
of solar and a good size diesel generator to extend your range plus a
smaller backup generator for safety. However, this boat also
reported
only getting about 30 hp equivalence with their SD15 motors. That
is a bit underpowered for our 46' catamaran, which really would work
best with two 55 hp motors. Based on their regeneration numbers
and reports on low amounts of horsepower, we had to think twice about
that being our main propulsion system.
Now let's talk about the first boat that was hit by lightning.
They had originally gone with the four SD15 motor configuration to get
enough horsepower for their large cat. They did report that his
was overkill for most situations, as two would get them by for normal
motoring.
However, after being struck by lightning, they decided to get rid
of two of their four SD15 motors and install
two diesel
engines. Now they can motor off of their two SD15s when they want
to, but have the diesel engines as backup for longer range when
extended motoring is needed. Also, in an emergency, they will
have more power. Finally, the diesel engines act as a backup to
the electric motors if their boat is struck by
lightning again.
So, based on the information gained from these two boats, we got
out
our pen and paper again and ran some numbers. We found two 7.5
kw, 48v, electric pod motors that run at higher RPMs (2,500). If
we ditch the SD15 motors and, instead, add these two smaller electric
motors, yet keep the existing
diesel engines while added two high power alternators (one for each
diesel engine) we could have the benefits of both systems.
This configuration will allow us to get almost all the benefits of the
electric
drive system. We could still motor at 5 knots on electric for
about 3
hours sending 3.75 kw to
each pod motor from the initial charge on the batteries. Plus, we would
get another 3 hours of motoring from solar recharge during a sunny
day.
That is
a total of 6 hours per single sunny trip, which would generally be
plenty
of motoring time, since we are a sailboat.
However, those two 7.5 kw
pod motors are nowhere near strong enough to deal with an emergency,
like
a stiff current
or lee shore in a strong wind. However, we would still have the
full
power of the 55 hp diesels to add to the pod motors when needed.
If we get hit by lightning, we still have the
diesels. As for other times, like entering and leaving port, we
have the electric motors, which are better for maneuvering and don't
need to be warmed up in the morning. They are also useful for
some regen, when the wind is blowing strongly, or for motor sailing, or
drogue effects,
etc. And, we still have big enough battery bank for air
conditioning all night, if needed. Finally, there are significant
fuel
savings in this configuration (see example passages, below).
And
another big bonus, the cost to add this system goes way down compared
to Plan A. We no longer need
the 20 kw generator, so that's $20,000 less right off the bat. We
don't have the
cost of pulling the old diesels (several thousand dollars). We
don't need Oceanvolt SD15
motors, which cost $18,000 each. We would need to replace them
with the two pods motors, but they only run about $9,000 each plus
another $1,000 each for hydraulics to lift them out of the water when
not in use.
That is a net savings of $16,000 just on the motors. Doing the
math,
that is a total savings of about $36,000 and we have a redundant
propulsion
system with 110 hp available from the diesel engines in emergencies and
two electric pod motors for when slow propulsion is advantageous.
However, there is no free lunch, so if we go with this, we must deal
with the weight penalty of 850 lbs. (100 lbs each for the
pod motors, arms, and hydraulic systems, and then we must add an
additional 650 lbs of batteries. That is
not an insignificant number on a catamaran and cats are
seriously affected by
weight. Fortunately, we plan to go with a production cat,
not a performance cat. Therefore, our load carrying capacity
soars up from something like 2,500 lbs to 9,000-13,000 lbs (depending
on the boat we pick).
However,
weight still matters. That means we will try to reduce weight in
other places. For example, on the Salina 48, we will lop off that
stupid rear
sun platform, which weighs in at about 400 lbs... and go with normal
davits. That's a good start. We can change the stainless
steel standing rigging to
synthetic, that saves about 80 lbs. And, we'll look for more ways
to reduce weight, exploring all
the viable options to
make this Plan B work. For example, if nothing else, we can
reduce the amount of diesel we keep on board, since we also have some
electric propulsion. Diesel weighs a lot! A gallon of
diesel weighs about 7 pounds, so if we reduce our diesel storage from
127 gallons to 84 gallons, we save that 300 lbs. However, at the
beginning of a long passage, if we want to start off with full tanks,
so be
it. With a minimum LLC of
9000 lbs, we can afford that temporary weight. We will burn away
some of that weight as we use up diesel on the passage.
Below is a comparison of passages on
Diesel Boat vs a Hybrid diesel/electric (Plan A and Plan B).
I'm going to hit the highlights, as we see it, and
show you why we are
considering making the change to add electric motors. The
comparison comes down to
these
two main factors.
1) On the diesel side:
Firstly, diesel
engines are far cheaper than setting up a hybrid and come with the
boat! Secondly, diesel engines
turning a prop are anywhere from 10% to 20% more
efficient than a generator supplying electric power to a motor turning
a prop.
Why the percentage range? It depends on the number of conversions
of energy. If you go directly from a diesel generator, without
going to the batteries first, you cut down on some of the
conversions. Hence, there is not as much of a penalty. At
the root, the extra cost of the system, the percentage loss of power,
and the overall extra horsepower are the
main factors which most proponents of diesel power
will use to argue against a Hybrid system.
And, they are correct about these factors! However, as
you will see, this isn't the whole story, there are many advantages for
an electric propulsion system as well.
2) On the hybrid or combination
side: The electric system obtains energy from several
sources, diesel fuel (generator or engines), solar
power, wind generators, and some from sailing regeneration
(more on what this is later and why is isn't a significant
amount).
Let's talk about solar first since it is the big one.
A catamaran comes
with a large surface area over the salon and cockpit. If
you also add on a stern arch (which we plan to do, see photoshopped
image at the bottom of the page),
specifically designed to hold more solar panels, it is possible to add
around 5 kWh of solar panels to a boat like the Salina 48 or Leopard
48.
Without enough solar, an electric/diesel boat is not as viable for
saving fuel.
Now, some people tell you that your panels will receive about 4
hours of their full rated maximum over a typical day, but we have
obtained real world numbers from several cruising boats who tracked
their charge rates over time. For example, one boat has 930 watts
of solar and gets about 5 kWh a day from that into the batteries (while
in the tropics).
That means,
on a typical sunny day, on a boat with 5 kWh panels, we will supply
about 24 to 25 kWh of
energy back into our batteries. This
does not take you quite as
far as you
might imagine, in fact, 25 kWh will only last for about 3 hours of
motoring at 5 knots (more on that below).
Here are the passage examples
that I will use:
1)
Short passages of less than 6 hours.
2)
Single day passages during daylight,
going 60
miles.
3)
Single day passages during night,
going 60 miles.
4)
Single day passages during daylight,
going 90
miles.
5)
Two day passages with two days of
sunlight, going
260 miles.
6)
21 day passages across an ocean, with
steady
trade winds, going 3,024 miles.
7)
21 day passages across an ocean, with
steady
trade winds, crossing the equator, going 3,024 miles.
8)
21 day passages across an ocean,
becalmed in the
middle for a week, going 3,024 miles.
For comparison sake
in these examples, here are the boats we are using (this data comes
from captains
on real boats):
1)
For the diesel boat we are using a 46' catamaran,
fitted with 54 hp
diesels. With one
engine running they reported burning only a half-gallon an hour at 5
knots. That's good fuel economy! Some cats report more like
3/4 of a galleon an hour. However, we'll go with this more
efficient number to give the diesel boat its best numbers.
2) For the Plan A hybrid, we are also using a 46' catamaran equipped
with the
Oceanvolt SD15 motors and Gori 3 blade folding props. At 5
knots they used 3.75 kw of power, each. Unlike the diesel, you
need to run both SD15 motors, so the total consumption was 7.5 kw.
3) For the Plan B hybrid, we will still use a 46' catamaran equipped
with two 7.5 kw electric pod motors and two 55 hp diesel engines.
The pods will still use 3.75 kw of power, each, or 7.5 kw total to push
the boat at 5 knots.
Note: I'm
getting numbers on the OV motors from two real world sources. One
captain's boat has one SD15 ServoProp and one SD15 with a Gori
propeller. He reports that the SD15 with the Gori prop uses, and
I quote, 'half the electricity at the same revolutions then the
ServoProp'. The other captain is running two SD15 ServoProps and
reports that running at 7 knots he uses 7.5 kw per SD15 ServoProps, 15
kw for
both. Now, for our fuel comparisons I am reducing the speed of
our catamaran to
5 knots, this will drop our ServoProp consumption numbers down to 3.75
kw for each motor, or 7.5 total. However, we know from the other
captain that you only use half that power with the SD15s using a Gori
prop. So, the total required output would be 3.75 kw.
However, just for arguments sake, let's assume it is the same
efficiency as the ServoProp. That means 15 kw (total) gets you 7
knots. Reducing to half speed (3.5 knots) would reduce your power
requirement by 8, so about 2 kw. But, if we only reduce from 7
knots to 5 knots, that should require about 7.5 kw
(total).
To get that number, I am using the standard
calculation of the required propulsive power increasing to the cube of
the speed. This means that to double your speed requires
eight times as much power. Or reducing your speed by half only
requires 1/8 the
power. So, reducing from 7 knots to 5 knots, all total, the
motors
use 7.5 kw to move at 5 knots. This
means, for a battery bank of 38.4 kWh, with a usable 25 kw, you can
motor for just about 3 hours (22.5 kWh) leaving 2.5 kWh for house needs.
That jives with the stats from another catamaran using a new Volvo
electric sail drive motor. They state that it travels 27 NM @ 5
knots on a 40 kWh battery. They are probably only using 80%
DOD. That would make their consumption about 7.4
kw. So, that is about the same, around 7.5 kw
(3.75 per motor) to motor at 5 knots which confirms our numbers.
For the primary generator on Plan A, we're using a 20 kw DC generator,
which
burns
1.6
gallons of fuel when outputting its maximum 20 kw of power.
However, figure a 20% conversion loss on generated power. The
example cat
will be equipped with a 38.4 kWh battery bank, allowing for
25
kWh
usable Lithium batter discharge (about 65% if we keep the charge level
between 20% and 85% to make the batteries last longer).
For the Plan B Hybrid, we add high output 48v alternators that put out
100A, or about 4.5 kw per hour, per motor running (again, losing 5%
when
sending that power to the batteries). We'll figure .75 gallons an
hour for a 55 hp diesel engine.
I am also using the 50% motoring rule, which means you sail 50% on a
typical
trip and motor the other 50%. This data is gathered from many
different captains.
Note, I am not figuring in any regeneration from sailing with the props
turning backwards in these examples since this is only viable on very
windy days or it slows the boat down too much and, therefore, doesn't
really save much fuel.
|
Example One:
Short Passage of Six Hours or less (36
nautical miles or less
trips)
This is a 6 hour trip, leaving at 8 am arriving at 2
pm.
Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of
the
trip, means 3 hours of diesel motoring, so 1.5 gallons burned.
Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and
sailing the other 3 hours means zero diesel used.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
Motoring on battery power for the first 3 hours and
sailing the other 3 hours. This means zero diesel was used.
Winner: Plan A or
Plan B Hybrid by 1.5
gallons per passage.
Example Two:
Single Day Passage During Daylight (60
nautical mile trip)
This is a 10 hour trip, leaving at 7 am arriving at 5
pm,
averaging 6 knots.
Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of
the
trip means 5 hours motoring, so 2.5 gallons was burned.
Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and
sailing for 5 hours followed by 2 hours of motoring off of solar
recharged batteries. This means zero diesel was used.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
Motoring on battery power for the first 3 hours and
sailing for 5 hours followed by 2 hours of motoring off of solar
recharged batteries. This means zero diesel was used.
Winner: Plan A or
Plan B Hybrid by 1.5
gallons per passage.
Example Three:
Single Day Passage During
Night (60 nautical mile trip)
This is a 10 hour trip, leaving at 10 pm arriving at 8
am,
averaging 6 knots.
Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of
the
trip means 5 hours motoring, so 2.5 gallons burned.
Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and
sailing for 5 hours followed 30 minutes the 20 kw diesel generator
running. Calculating a 20% conversation loss, they send 7.5 kw to
the motors while sending about 10 kWh to the batteries. They can
then motor on battery power for the final hour. We used 0.8
gallons of diesel, though they arrive with very low batteries.
Plan B: Combo Pod
motor and diesel Hybrid Cat:
Motoring on battery power for the first 3 hours and
sailing for 5 hours followed 2 hours motoring on a single diesel
engine. This sends just 9,000 watts back to the batteries (200
amps) for house uses and maneuvering when we arrive. We used 1
gallon of diesel.
Winner: Plan A Hybrid by
0.2
gallons per passage better than the Plan B Combo boat and 1.7 gallons
better than the diesel engine only boat.
Example Four:
Single Day Passage During Daylight (90
nautical mile trip)
This is a 15 hour trip, leaving early at 4 am (dark)
and
arriving at 7 pm (sunset).
Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of
the
trip means 7.5 hours motoring, so 3.75 gallons was burned.
Plan A: OV Hybrid Cat:
Motoring for the first 3 hours on batteries. Then sail during the day for 7.5 hours, recharging the
batteries via
solar. Then they motor on electric for another 3 hours.
At the
end of the trip, they fire up the generator for an hour
while recharging
the batteries about 10 kWh. The motor on battery power for the
last half hour. They used 1.6 gallons of
diesel.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
Motoring for the first 3 hours on batteries.
Then sail during the day for 7.5 hours, recharging the batteries via
solar. Then they motor on electric for another 3 hours.
At the
end of the trip, they fire up the diesels for 1.5 hours of motoring
while recharging
the batteries some for House needs. They used 1.13 gallons of
diesel.
Winner: Plan B Combo boat
by 0.47
gallons per passage better than the Plan A hybrid boat, and 2.62
gallons better than
the diesel engine only boat.
Example Five:
Two Day Passage with Two Days of Sunlight
(260 nautical mile
trip)
This is a 43.5 hour trip, leaving at 11 am, arriving
on
the
second day at 5:30 am.
Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of
the
trip means 21.75 hours motoring, so 10.89 gallons was burned.
Plan A: OV Hybrid Cat:
They motor the first 3 hours on
batteries, then
regain 25
kWh, via solar recharge, each of the two days. That is a total of
50 kWh which is about 6 hours of motoring
time. All total, they will motor off batteries for 9 hours on
this voyage. That
still leaves about 12.75 hours out of the total 21.75 that they
need
to motor. They
run a diesel generator for 2.5 hours, sending 25 kw to the
batteries then motor for 3 hours off the battery charge. That
leave them with 7.25 hours motoring still required. They run the
generator for 2.5 hours and motor off batteries again for 3
hours. Now they are 1 and 3/4 hours motoring from their
destination. They run the generator for one hour and motor off
batteries for the final 3/4 hours. All total, the generator
ran for 6 hours, so they burned 9.6 gallons of diesel.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
They motor the first 3 hours on
batteries, then
regain 25
kWh, via solar recharge, each of the two days. That is a total of
50 kWh which is about 6 hours of motoring
time. All total, they will motor off batteries for 9 hours. That
still leaves about 12.75 hours out of the total 21.75 that they
need
to motor. They
run a diesel engine for 6 hours, sending 27 kw to the
batteries from the alternator. They switch back to the pods and
go for 3
hours on batteries. They are still 3.75 hours short, so they motor for
3 hours, sending 13.5 kw to the batteries, then motor for one hour
(leaving some for House uses). All total, they
ran one
diesel engine for a total of 9 hours, so they burned 6.75 gallons of
diesel.
Winner: Plan B Combo boat by 2.85 gallons per trip over the Plan A
Hybrid and 4.14 gallons over the Diesel boat.
Example Six:
21 Day Passage crossing the Atlantic, with
Steady Trade Winds (3,000
mile trip).
Being typical a Trade Winds crossing, we can figure
that we will only have to motor for two 3 hour stints, like early
morning or during the night.
Diesel Cat:
Burning at .50 gallon an hour, for 6 hours a day for
21
days equals 63 gallons of diesel.
Plan A: OV Hybrid Cat:
They motor the first 3 hours on
batteries. Then they charge up 25 kWh via solar power, each day,
allowing them to motor for another 3 hours each day. This
covers the motoring needed for the first day but they need an extra 3
hours each day thereafter. They
run their diesel generator for 2 hours each subsequent day, putting 15
kWh into the batteries. They use 7.5 kWh to motor the final hour
needed and the other 7.5 kWh for House needs.
They ran their
diesel generator for 2 hours for 20 days, or 40 hours total. At 1.60 gallons an hour that equals a total of
64 gallons burned.
Plan B: Combo Pod motor and
diesel Hybrid Cat:
They motor the first 3 hours on
batteries. Then they charge up 25 kWh via solar power, each day,
allowing them to motor for another 3 hours each day. This
covers the motoring needed for the first day but they need an extra 3
hours each day thereafter. They
run one diesel engine for 2.5 hours each subsequent day, putting 11.25
kWh into the batteries. They use 3.75 kw for the final half hour
of motoring off electric, leaving the rest for house needs. They
use their diesel engine for a total 50 hours.
At
.75 gallons an hour that equals a total of 37.5 gallons burned.
Winner: Plan B Combo boat by 26.5 gallons per trip
over the Plan A Hybrid and 25.5 gallons less than the Diesel only boat.
Example Seven:
21 Day Passage crossing the Equator,
with Steady Trade Winds
(3,024 mile trip).
This
is a bit of a different trip. With the Trade Winds, you only need
some minor motoring. For sake of argument, we
will still figure in motoring for the
occasional 3 hour stints, like early morning. That,
and this time, we will calculate in the crossing of the equator as 3
days of
no wind.
Diesel Cat:
Burning at .50 gallon an hour, for 6 hours a day out
of
18
equals 54 gallons of diesel. Plus, three
days of motoring 24 hours a day is 36 gallons additional for a total
burn of 90
gallons.
Plan A: OV Hybrid Cat:
They motor the first 3 hours on
batteries. Then they charge up 25 kWh via solar power, each day,
allowing them to motor for another 3 hours each day. This
covers the motoring needed for the first day but they need an extra 3
hours each day thereafter. They
run their diesel generator for 2 hours each subsequent day, putting 15
kWh into the batteries. They use 7.5 kWh to motor the final hour
needed and the other 7.5 kWh for House needs. All total, they ran
their generator during those 17 days for 34 hours.
However, on three days they were becalmed in the
doldrums. During
those three days they must motor 24 hours a day instead of six. They
still regain 3 hours of motoring from solar
each day, leaving 21 hours of remaining motoring still needed each day. While
running the generator, 7.5 kw goes to the motors to keep moving while
10
kWh gets stored in the battery bank per hour. Recharging the
batteries takes 2.5 hours. So,
each 2.50 hours they regain a full charge allowing 3
hours of motoring. To motor that extra 21 hours requires about
four such cycles, per day, which alsoleaves
them enough extra power for house uses. So each day they motor
for 10 hours with the generator running burning 16 gallons of fuel, or
a total of 48 gallons. They add that to the other
17 days where they only had to run the generator for 2 hours a day,
which equals 34 hours and they get a total run time of 64 hours,
or 102.4 gallons of fuel burned.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
They motor the first 3 hours on
batteries. Then they charge up 25 kWh via solar power, each day,
allowing them to motor for another 3 hours each day. This
covers the motoring needed for the first day but they need an extra 3
hours each day thereafter. They
run one diesel engine for 2.5 hours each subsequent day, putting 11.25
kWh into the batteries. They use 3.75 kw for the final half hour
of
motoring off electric, leaving the rest for house needs. They use
their diesel engine for a total 42.5 hours.
At
.75 gallons an hour that equals a total of 31.88 gallons burned during
those 17 days.
However, on three days they were becalmed
in the doldrums. During
those three days they must motor 24 hours a day instead of six. They
still regain 3 hours of electric motoring from solar
each day, leaving 21 hours of remaining motoring still needed each day. While
running one diesel engine, 4.2 kWh gets stored in the battery bank per
hour. Every two hours they gain 1 hour of electric motoring (with
some left for house needs). So, they run on the diesel engine for
14 hours and electric motor for 7 hours. All total, they run the
diesel engine for 42 hours during those three becalmed days. At
.75 gallons an hour, they burn 31.5 gallons. Add that to the
31.88 gallons from the other 17 days and you get a total diesel usage
of63.38 gallons.
Winner: Plan B Hybrid by 39 gallons per trip over the Plan A
Hybrid
and 26.62 gallons over the Diesel boat.
Example Eight:
21 Day Passage crossing the Equator,
becalmed for seven days
(3,024 mile trip).
Diesel Cat:
Burning at .50 gallon an hour, for 6 hours a day out
of
14
equals 42 gallons of diesel. Plus, seven
days of motoring 24 hours a day when becalmed is 84 gallons for a total
burn of 126
gallons.
Plan A: OV Hybrid Cat:
Everything is the same as the voyage above, but now
they use their generator, burning 3.2 gallons a day for 13 days and 16
gallons a day for 7 becalmed days. That totals
153.6 gallons burned.
Plan B: Combo Pod motor and diesel Hybrid
Cat:
Everything is the same as the voyage
above, but now they run one diesel for 13 days for 2.5 gallons (32.5
gallons). Plus,
for seven days,
they have to run one diesel for 14 hours a day, using 73.5 gallons
during the 7 days becalmed. That plus the other 32.5 from the 13
days
is 106
gallons total.
Winner: Plan B Hybrid
by 47.6 gallons per trip over
both the Plan A Hybrid and 20 gallons less than the Diesel only boat.
Important note on reducing
speed:
With either electric motoring option, you can alway sacrifice
speed for distance. Though you can reduce speed on a diesel
engine, it is most efficient to run them at certain minimum RPM, so
going very slow is not as efficient. This is not true of electric
motors, which run fine at any speed, even the slowest. The rule
about power is such, and I quote, "For a displacement boat making way
through the water, the required propulsive power increases in
proportion to the cube of the speed." This means that if you want
to double your speed, you need eight times as much power or,
conversely, to go half the speed your boat requires eight times less
power.
If
you reduce your electric motors speed to half, for
example, going from 7.5 knots to 3.75 knots, your batteries which
motored you for 2.5 hours will now motor for 20 hours. So,
technically, if you slow down enough, like to 3 knots, you don't have
to burn any diesel on a long
becalmed voyage if you don't want to, all you have to do is sacrifice
time for distance and let the solar panels recharge the batteries.
Example Passages, Our Conclusion:
In the examples we listed, the Diesel boat always burns more diesel
fuel than the Plan B boat and in all but two cases when compared to
Hybrid Plan
A (the two exceptions are the becalmed for 3 or 7 day ocean
crossings). However, when comparing
just the two Hybrid plans, the Plan A only ties in short voyages and
loses to the Plan B in mid range or longer passages.
Therefore, when it comes to fuel savings, the Plan B boat wins, hands
down. If
you figure in the additional $46,000 initial cash outlay, the Plan A
boat is far more expensive! Hence, we plan to go with Plan B.
|
Diesel Boat has Greater Range Myth:
One
thing we keep reading from forums or hearing on
Youtube
videos is that diesels have greater range than a hybrid electric or
combo electric/diesel boat
due to the diesel fuel being more energy dense and conversion losses in
an electric hybrid system. This is just
not true, assuming you use a large enough
solar array. Let's use the same 48' cat with 55 hp diesels
against our Hybrid or Combo options.
1)
Diesel Boat: Let’s say your boat has a
100
gallons fuel tank and uses 0.75 gallons an hour at 5 knots. That means the diesel boat can motor for 133
hours, or 666 nautical miles.
2) Hybrid Boat, Plan A:
The first day we get a
free 3 hours of motoring (about 15
miles) plus 15 from solar recharge. Each additional day we get 3 hours
of motoring from solar
recharge of
the batteries, for another 15 miles. The two electric
motors
use a total of 7.5 kw to push the boat at 5 knots. You
have to
run the generator for 2.5 hours to recharge the battery bank (7.5 kw
goes to the motors
and 10 kWh gets stored in the batteries). This will recoup
the 25 kWh you used from the batteries. During that recharge
time you travel 12.5 nautical miles. Then, you get to motor
for 3 hours off of the recharged batteries, going and additional 15
nautical miles
without the generator running.
So, about every 5.5 hours, you
travel about 27.5 miles and burn about 4 gallons of diesel.
Converting this to a day, you use about 17.44 gallons a day to travel
120 miles. With
100 gallons you go about 5.75 days before running out diesel. Of
course, you also get
to add the extra 12.5 miles from solar each day, going an additional 72
miles during that period. Finally, add the initial 30 miles
you went on batteries the first day. All total, you travel about
792 miles, about 126 miles more than the pure diesel boat on the same
amount of diesel fuel.
3) Combo Boat, Plan B: With
our diesel engine/electric pod hybrid, things are even more
interesting. Each day we get 3 hours of pod motoring from solar
recharge. Then, we use a single diesel engine for about 6 six
hours and
recharge the battery bank (and add some
energy for House needs) and then motor for 3 hours on
batteries. So, each day we use the diesel engines about 16 hours,
burning 12 gallons of fuel. If we divide that into the 100
gallons the example boat carries, we get just over 8 days. At 5
knots,
you travel 120 nautical miles a day, so we go 960 miles before we run
out of fuel. As you can see, our range from a Plan B boat is far
more! This is due to recharging batteries from solar and while
motoring we use the more efficient diesel engine (compared to loses
with a generator system). This is not a surprise, we get the best
fuel mileage advantages of a diesel boat and the best advantages of an
electric boat. (NOTE: this does not factor in added weight of 850
lbs for the electric system, so that may lower this fuel savings a bit).
However, we're not a motor boat, we're a
Hybrid sailing boat!
In
either Plan A or B, if we only have to motor for 3 hours a day while
sailing the rest, our range is unlimited since we get that from solar
recharge. The diesel boat will, eventually, run out of
fuel. This is not
perpetual motion, we are gaining fuel from the sun.
What about extended stays in areas with no
fuel stations?
This
is even more advantageous to the hybrid or combo boat. On these
electric boats, time
equals fuel. Every time you sit in some atoll, enjoying your long
stay, your batteries are being filled by solar power, in essence,
refueling your boat. Diesels get no additional fuel in these
remote locations.
On a Hybrid, your range and, therefore, time in these remote areas is
extended to
as long as you have food to eat. You can even keep moving from
island to island. Your range is vastly extended by free solar
'fuel' for propulsion or House needs.
So,
as you can see, the ‘diesel
has greater range’ is a myth. All it takes for a Plan A or B boats to
exceed
the range of a diesel boat is sufficient solar panels on board. In
our
case, we plan the same 5 kWh total from our panels as in these
examples. As for the Plan B hybrid, it just has greater
range than either other option since it has the advantages of both the
diesel boat and a hybrid boat!
|
Regeneration
What
we are talking about here is letting the props turn backwards as the
water moves past,
generating power back into the batteries. In essence,
turning wind power (on the sails) into electricity stored in the
batteries. Using the Oceanvolt ServoProp system, you could expect
to get
about 1
kWh per motor while sailing at about 8 knots. This is slightly
above the average
sailing speed for our type of comfortable catamaran (see chart
below for how much regeneration at what speed).
However, each motor will slow the
boat by a half knot, so that's a full knot if both props are used to
regenerate! There is no free lunch.
A full knot means
that over a long passage of something like 21 days, if you
regenerate,
for say, 12 hours a day, it means you lose a knot
per hour over 12 hours, or nearly 14 miles of travel a day. When
you multiply that times
21 days, that's 294 miles. That equals another two full
days of travel
added to
your passage! If you figure you must motor for half of those
two extra
days, you burn fuel. It also takes you an
extra two days on the ocean to reach your destination.
|
 |
|
But,
not so fast. There are some ways to make regeneration more
efficient. One is
to only regenerate while your boat has enough wind to take it over
efficient hull
speed (the speed in which your boat now requires more energy to gain
the same increase in speed). Example: If your boat sails at 5
knots in 10 knots of wind, and 8 knots in 16 knots of wind, but
suddenly requires 24 knots of wind to go 10 knots of speed (no longer
achieving half of wind speed), your efficient hull speed is something
just over 8 knots.
This means that, once you have enough wind to push your boat over 8
knots of hull speed, and you choose to regenerate, there is likely
enough wind to
keep you sailing at that same 8 knots (hull speed). Basically,
you are wasting
some of that wind energy trying to push your boat beyond your efficient
hull
speed. So, instead, you could spend that wind power on
regeneration.
However,
this means you will only be regenerating while the wind is blowing
something like 20 knots or more (in this boat's hull speed
example). That doesn't happen all that much on a typical trade
wind passage, especially with a slower production catamaran.
However, if you only regenerate during these
periods of strong wind, you won't likely add much more
time to your trip, yet you will regenerate (and, possibly, at even more
than the
1 kw/motor gain).
However, remember, if the wind is blowing strongly enough to use
regeneration, it is also blowing strongly enough to sail and not be
motoring. Therefore, you aren't using energy sent to the motors
and don't need that regeneration power since the solar panels will do
the job to keep up the house uses and recharge the batteries to full
anyway. You might as well just sail
slightly faster.
Due to this, we don't really plan to use regeneration very often.
If we are sailing in strong winds and the batteries are low, we might
do it then, but when the batteries are charged up, why bother?
Slowing Down
There are times when you want to reach a destination at a specific
hour, like morning, as the sun is rising. Getting there too soon
means entering in the dark. If the wind comes up too much, on a
diesel boat, you would have to reduce sail to slow down. However,
in the case of an electric boat (Plan A or B), we can use one or both
electric motors in
regeneration mode to slow us down slightly while leaving the sails
up.
If that's still not enough speed reduction, we reduce some sail, yet
keep
regenerating. The added benefit here is that we get a little
power
regeneration while we slow down to arrive at the right time. This
also works well with a standard SD15 (you don't need the ServoProp
motors for this benefit).
|
Drogue effect:
Another advantage to regeneration, especially when sailing on a
catamaran, is the drogue effect. In bigger seas, as you surf down
the face of a swell, catamarans can pick up too much speed and then
their bows pierce into the face of the next swell. Often,
catamarans will deploy a drogue to slow them down. If you put
both of your electric motors into regeneration mode, with just the
right amount of forward throttle, they will slow you down a knot
as the boat surfs down the wave, however, as the boat starts to climb
the next face, the motors will power you up. This effect evens
out the speed of the boat, somewhat, and gives you some charging of the
batteries as well (though, typically, you will burn more than you gain,
but it will extend your motor sailing range). If you are still
surfing too swiftly down a wave, add a drogue. We went one of the
adjustable types so we can tailor the drogue effect work with the
electric motor drag.
|
Motor Sailing
While sailing we also have the option of motor
sailing. This is quite a bit different than a diesel boat motor
sailing. Typically, on a diesel boat, once the wind drops to the
point where you are only going 3 or 4 knots, most sailors take down
their sails and just motor at 5-6 knots. The reason is simple,
the wind isn't going to help them anymore if the diesels are pushing
you at 5 knots and there is no point to
running a diesel at a low RPM. That is bad for the diesel and
isn't going to save you much fuel anyway. You might as well put
them at their optimum fuel efficient RPM and do that 5-6 knots.
Motor sailing with an electric motor is different. Electric
motors have
full torque at any RPM. Therefore, you can just give them a
little power and add, say, 1 or 2 knots to your boat speed, while
continuing to sail. At that low of a power draw, our battery bank
can go for something like 24 hours. Now you can keep the sails
up, adding a knot or two to the motoring speed, getting you
to 3 or 4 knots of total speed, without burning diesel fuel. |
Wind Generators
These
are small turbines on a pole, driven by props turned by the wind.
At maximum rated power, they seem like a pretty good choice for making
power, but not so fast. First off, you can't trust the
manufacturer's numbers. They use a constant stream of wind in a
wind tunnel, you probably won't see those same numbers in the real
world where the wind is more fickle. Secondly, those maximum
power numbers are for high winds. For example, in the chart
(below) you can see that at 20kt of wind the various manufacturer's
models listed output between 140-280 watts per hour.
However, if you are a cruiser circumnavigating the world (like us), and
typically going down wind with the trade winds, then seeking sheltered
anchorages out of the wind, you aren't going to see a lot of days with
that kind of sustained wind. On average, you're more likely going to be
down in the 1 to 12 knot category. Even at 12 knots, the output
is only 20-55 watts and below 4 - 6.8 knots of wind you aren't getting
any. So, you are only going to see a small amount of energy gain
most of the time. A single 330 watt soler panel is going to gain
a kilowatt in the five hours it is in sunlight, just about matching
what
a wind generator will output in 24 hours in 12 knots of sustained wind.
If you don't have room for more solar, a wind generator could make some
sense.
But, don't forget, wind generators do make noise as they turn, there is
a slight danger of spinning blades, and they require eventual
maintenance since they have moving parts. There is also a
significant cost to buy one.
After
considering all this, we haven't yet decided if we want one or even two
wind generators on board. If you think about all the days of less
than 12 knots of wind, overall, we will gain more power from a
additional solar
panel than from a wind generator, with no noise. Sure, there
will be days when the sun is blocked yet there is significant wind, and
we won't get that solar power, but the number of those days are
infrequent,
so in those cases we could just run the 20 kw generator for a short
period. Example: if the wind is blowing at 20 knots, a typical
amount of gain from the wind generator is 200 kw, or 4.8 kWh in a 24
hour period. We can run the generator for fifteen minutes and get
the same thing. That is only fifteen minutes of generator noise,
then quiet,
or 24 hours of hearing those turbine blades. Yes, that costs us
about a half gallon of fuel, but we won't have to do that very often
and at a savings of a half galleon of fuel only per time, it would take
something like 700 days of doing this to repay the price of buying the
wind generator!
We'll look into this further before making a final decision on one or
more wind generators, but as of now, we're leaning toward skipping
these on S/V Lynx.
|
 |
| Turbine |
Silent-X |
Air
Breeze |
D400 |
Superwind |
Silentwind |
Rutland
1200 |
Rutland
914i |
Nature
Power |
|
Max power (W @
12V)
|
450
|
250
|
600
|
350
|
420
|
483
|
450
|
400
|
|
Wind @ max (kt)
|
25
|
22
|
37
|
24
|
28
|
29
|
39
|
24
|
|
20kt output (W)
|
200
|
230
|
192
|
180
|
140
|
255
|
135
|
280
|
|
|
12kt output (W)
|
40
|
50
|
48
|
20
|
45
|
60
|
40
|
55
|
|
|
Cut-in speed
(kt)
|
6
|
6
|
5
|
6.8
|
4.2
|
4
|
5.8
|
6.1
|
|
|
Combo
Electric vs Diesel vs Hybrid Conclusion:
To quote a boat owner who has
sailed their cat around the world for
five years, he stated, "The single most important thing
on our boat is power. You cannot have enough."
Or, another boat owner who said, "We have a very large battery bank,
large
enough to run the air conditioning for half the night." Their
battery bank is less than 10 kw. With 25 kWh of usable power from
the 39,400 bank we can
run
our
air conditioners all night, silently, and recharge the batteries in the
morning.
All
total, over all passages we make on our epic voyage, we could save over
11,000
gallons of fuel (this is a rough estimate, using the two leopard boat
numbers, though our boat will be
slightly different. That’s the estimate on how many
gallons we save
using a combo boat over a diesel engine only cat on our particular
voyage.
You also get rid of all the costs, dangers, and
hassles of propane,
since you are
an electric boat, you use all electric appliances, no propane. So, no time carting them ashore, finding a
compatible fill nozzle, going back to pick them up later (in many
cases) and
paying for propane.
Those are a lot of hassles you either avoid or
reduce.
However, currently, the cost to upgrade to a Plan A
hybrid
boat is too steep! It will take more nearly 10 to 16 years to
recoup
the
initial expenditure (depending on if and how much diesel goes up).
Fortunately, the Plan B option is much less initial
expenditure ($46,000 less). Therefore, we could recoup that
expenditure in more like 4-6 years.
Why is it worth even the $30,000
initial outlays of cash?
Comfort!
Here are the comforts we get by
having the electric system on board (batteries, solar, etc.):
1)
We will be able to run our air-conditioning,
all night, while we are anchored in a hot and humid place, without
turning on the
generator.
2)
The extra stored energy means we can make more
water and, therefore, take more showers.
3) During
our double circumnavigation, we
save endless time and energy in not having to, find, cart, pour, and
filter over 1000
jerry cans of
diesel fuel into our tanks.
4)
We save 23,000 hours of not
smelling exhaust.
5)
We save the same 23,00 less hours of having to listen to a
diesel engine.
6) We are
more self-sufficient, able to remain away from civilization for longer,
without needing diesel.
7)
We’ll spend less
time going to fuel
docks.
8)
We spend no time searching to find or fill propane bottles.
9)We
spend less time
doing
maintenance on diesel engines and sail drives (mostly due to running
the generator or diesels a lot less hours, so maintenance cycles are
further apart).
10)
We
can motor sail (silently).
11)
We can use regeneration for a drogue effect to even out the motion of
the boat.
12)We
have instant power at any time without warming up the diesels.
This is good in port, and may help to complete a tack. Even if
the pods are raised, it takes less than 20 seconds to put them in the
water with the hydraulic system we will use.
13)
We save time and fuel not having to warm up two diesel engines every
time we leave port.
14)
We have more power for charging all our toys.
So, how do you put a price on
comfort? If
we have to cough up $30,000 extra to refit the boat for Plan B... so be
it! Most, if not all, of that initial
coast will be regained in the first 5 years and we will save money in
the long run.
However, we expect prices to come
down in the next three years, so maybe this initial cost will become a
bit less.
Comparing the two Hybrid Plans,
Plan B is far less for initial cash outlay and saves more money in the
long run, but adds weight to the boat. Then there is the safety
issue. When it comes to safety concerns,
the Plan B boat wins, hands down. After all, it has two separate
propulsion systems which can combine to have more power than the
diesels and far more than the Hybrid Plan A. It is also safer if
we
are hit by lightning. On the down side, the Plan B boat has more
maintenance costs (one additional diesel, since it has two engines and
a generator vs two generators). It also has two sail drives that
need
serving.
Still, the Plan B Combo boat seems to be the better option, cheaper and
safer, yet retains most of the advantages of a Hybrid system boat.
So, currently; based on the
comforts
gained, safety, and cost, Plan B is the route we will choose to go
during our
refit of S/V Lynx. However, here are the two system setups (Plan
A and Plan B):
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The Plan A Hybrid Setup for S/V Lynx (this
is now our 2nd choice; see Plan B below for our 1st)
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1) Two Oceanvolt SD15 electric
sail drive motors with Gori props:
Oceanvolt SD15
Synchronous permanent magnet electric motor.
Sail Drive with 1.93:1 reduction.
Lightweight: weighs as little as 42.5kg (motor & sail drive).
The only complete electric inboard propulsion system with
EMC certified closed circulation liquid cooling providing both cooling
and lubrication.
Functions as a hydro generator to generate power while under sail.
Gori three blade folding
prop:
We wold go with a couple these with a Gori folding prop, to quote their
site,
"The 3-blade Gori folding propeller marks a technological and
functional leap forward in the development of propellers for sailboats.
It is now possible for sailboats and motorsailers to gain the folding
propeller's speed advantages under sail, combined with the fixed
propeller's thrust capability when motoring. The 3-blade Gori folding
propeller was introduced on the market in 1994 and won the DAME award
and HISWA award the same year, as the best new marine product.
"OVERDRIVE" FUNCTION
The 3-blade Gori folding propeller's "overdrive" function adds a new
dimension to sailing under power. The helmsman can choose the propeller
pitch and profile in the water while sailing forward, by regulating the
yacht's shift and throttle control. Without the use of vulnerable
hydraulics or complicated mechanical devices.
The "overdrive" is used when motorsailing in fair weather or when using
the engine under sail. The "overdrive" gives the same speed at lower
rpms. The result is less engine noise, less vibration and better fuel
economy."
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2) 38,400 kWh lithium battery bank:
This
number isn't random. The typical amount of
energy we could recoup in a day of good sunlight is 25 kWh which is
also the usable power from this size bank, if we keep the batteries
between 20% and 85% charge.
With
a single sunny day at anchor, we can
net 25 kWh of solar, which refills our bank completely. Assuming
we are using power for a lot of house needs, certainly in 2 days we can
recoup a full battery charge for the
next voyage using just
solar regeneration.
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3) Five kilowatts of solar panels:
Solar panels are critical to the Hybrid system being
viable.
You must regain a lot of power from the sun or you are just burning
diesel up through a less efficient generator. To that end, if we
go with a Salina 48 or Leopard 46, we plan to build a
special stern arch. This will extend the coach roof line.
We are also adding a hard top over the helm, which will add a
little more space for solar panels. These are being added to
increase our total solar panel array. On the Salina 48, we can
get to over 5 kw.
On the right are two photoshopped images of a Salina 48, showing the
arch we plan to add to the stern. This arch will not increase the
length
of the
boat, since it ends at the same distance out as the sugar scoops.
To keep the weight down, we plan to build this out of carbon fiber.
We will also squeeze in panels on the regular coach
roof and Helm roof.
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4) One 20 kw and One 10 kw (or slightly
smaller) Diesel Generators:
The 20 kw (closer pic to the right) is the main
workhorse, which can
push the
boat to 7.5 knots, running both SD15 motors if needed or supply power
to the battery bank as well
as the motors when running at 6 knots or less. This generator
weighs 320 lbs.
As a backup, there will be a lighter 10 kw generator (farther pic to
the right),
capable of sending 5 kw to each motor to push the boat at 4 knots or,
while at anchor, we can run this generator to recharge the
batteries or run the A/C saving some fuel since we don't need the power
of the big 20 kw generator. This
generator weighs a maximum of 260 pounds if we go with the 10 kw
generator. (We hope the boat we buy comes with the smaller
generator already).
In an extreme emergency, after battery power is exhausted, we can run
both electric motors at
maximum thrust by running both generators at the same time, giving us
30 kw, supplying 15 kw to
each
of the two SD 15 motors. They can then run, flat out,
for as long as the diesel fuel holds up.
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5) Diesel Fuel tanks
We plan to keep the existing diesel fuel tanks, (127
gallons on the
Salina 48, 185 gallons on the Leopard 48, and 248 gallons on the Saona
47). Most of the time these
will be kept fairly empty, holding perhaps 50 gallons of diesel for
emergencies since most of the time we will run without any diesel usage
at all. However, when facing a long passage, or a long time away
from civilization, we can top off the tanks. Sailing with just 50
gallons of diesel saves a lot of weight! On the Salina 48 it
saves
us 539
lbs, on the Leopard 48 is saves 945 lbs, and on the Saona 47 it saves
us 1386 lbs.! The two generators
plus the batteries and SD 15 weigh a total of 1095
lbs. Or, if you look at the Salina 48, after removing the diesel
engines and sail drives, and reducing to 50 gallons of diesel, even
with the entire hybrid system on board the boat weighs 339 pounds
less, the Leopard 48 weighs 745 lbs less and the Saona weighs 1186 lbs
less!
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The Plan B Hybrid Setup for S/V Lynx (and
our current top choice)
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PROPULSION:
Two Aziprop 7.5 kw Fischer
Panda Pod motors
2500 rpm
28 Nm
48 volt
18.7 kg (41pounds)
These electric pod motors will be used for the majority of our
propulsion needs. Here are examples:
1) When entering or exiting port, or moving around an anchorage.
They don't have to be warmed up, are virtually silent, and have
excellent low speed properties since electric motors have full torque
at zero RPM.
2) During a passage when we want to motor sail. They put out no
fumes are virtually silent, and at low power usage can go for a very
long time on batteries.
3) For limited motoring when the wind drops (up to about 3 hours).
4) For regeneration, drogue, and just slowing us down (on purpose), on
some occasions.
To cut drag, these pod motors will be mounted on arms that are raised
with a hydraulic motor. Here is a link to a video showing a
system that does this (these are no longer sold though, but we will
make a similar system).
https://www.youtube.com/watch?v=nl1a_ACQmvs
Two Yanmar or Volvo 55 hp
diesel engines
These engines will come with the boat. These will rarely be used
compared to the electric pod motors. We plan to use the diesel engines for
three purposes:
1) On a long passage where we must motor for more than three hours,
continuously, as the diesels are more efficient in fuel use than a
generator supplying power to an electric motor.
2) To heat water and charge batteries using a High Output alternator while motoring.
(100 ah at 48 volt, one on each engine)
3) In emergencies, when high power and thrust are needed, like when fighting a
current or in a large blow with a lee shore.
FlexoFold three blade
folding
prop:
When
it comes to the diesels, based on reviews and tests, we plan to use
Flexofold 3-Blade sail drive Folding propellers. The strengths of
these props are as follows:
1) Low drag: Compared to fixed props, these folding props increase the
sailing speed of the boat by 1 to 2 knots (since there are two of these
in the water all the time).
2) Maximum Speed: They are the highest rated for speed of all the
folding and feathering props we have seen in tests, up to a knot faster
than the competition. (See test result below)
3) Pulling power in forward (bollard test): Again, they achieved
top marks in this test, which means when we are fighting a headwind,
going against a current, etc, these pull the boat forward better than
other options. (See test result below)
4) Simple: Compared to feathering props, these are simpler to maintain
and have less cost in rebuilds.
To the right are the 2015 Yachting Monthly posted results from their
tests on speed and bollard pull ahead:
Note, though stopping power wasn't as good as some of the other props,
that is not as much of an issue with our boat since we also have two
electric pod motors to aid in bringing the boat to a stop when needed.
On folding props:
Though we were interested in the Gori props, research shows that using
them on a sail drive is hard on the transmission if you try to use
their 'overdrive' feature, which requires you to go from reverse to
forward without stopping in neutral first. With the electric
drives this was less of a concern.
Also,
though there have been reports of both Gori and Flexofold props
coming off in rare cases, the Flexofolds have more mechanisms for
keeping the prop on the shaft where the Gori props only have two,
tightening the bolt and using loctite. The Flexofolds have these
two methods plus a metal tab washer with a nut and bolt system that
bends
the metal washer to keep either the bolt or the separate nut from
backing out.
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2) 38.4 kWh lithium battery bank: (800ah at 48volts)
This number isn't random. The typical amount of
energy we could recoup from solar in a day of good sunlight is 25 kWh, so recharging a 38.4 kWh 70% is very doable since you
won't ever completely deplete it.
In just one sunny days at
anchor, netting 25 kWh of
solar, we can recharge and are good to go. However, with House
needs, we will often spend two
days at anchor before any long passage or use the generator for a short
time to top off the batteries. But, when we have time, in 2 days
we can
recoup a full battery charge for the
next voyage using just
solar regeneration.
We have not settled on exactly which batteries we will buy yet, but are
leaning toward LifePO4, DIY option (see Solar and Batteries). But,
we are hoping for better choices in the next couple of years as battery
technology changes and prices continue go down (hopefully).
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3) Five kilowatts of solar panels:
Solar panels are critical to the Hybrid system being
viable.
You must regain a lot of power from the sun or you are just burning
diesel up through a less efficient generator. To that end, if we
go with a Salina 48 or Leopard 46, we plan to build a
special stern arch. This will extend the coach roof line.
We are also adding a hard top over the helm, which will add a
little more space for solar panels. These are being added to
increase our total solar panel array. On the Salina 48, we can get slightly more than 5 kw.
On the right are two photoshopped images of a Salina 48, showing the
arch we plan to add to the stern. This arch will not increase the
length
of the
boat, since it ends at the same distance out as the sugar scoops. We will also squeeze in panels on the regular coach
roof and Helm roof (see image, right).
NOTE: even though the original sun deck is shown in
these images, if we go with a Salina 48 we plan to remove that deck
completely and add a different dinghy lift system.
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4) One 10 kw (or slightly
smaller) Diesel Generator:
Our
9 - 10 kw generator is for use while we are at anchor if we run out of
battery power. The generator can run the A/C or recharge
our batteries of the solar isn't keeping up. We hope to buy a
boat that comes with
this smaller
generator already, but will add one if needed.
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5) Diesel Fuel tanks
Because we are keeping the diesel engines and a
generator, we will need the existing diesel fuel tanks, (127
gallons on the
Salina 48, 185 gallons on the Leopard 48, and 188 gallons on the
Leopard
46). Some of the time these
will be kept less than half full, holding perhaps 50 gallons of diesel
for
emergencies since most of the time we will run without any diesel usage
at all for short trips and very little for midrange passages.
However,
when facing a long passage, or a long time away
from civilization, we will top off the tanks.
Sailing with just
50
gallons of diesel saves a lot of weight! On the Salina 48 it
saves
us 539
lbs, on the Leopard 48 is saves 945 lbs, and on the Leopard 46 it saves
us 966 lbs.! This offsets the weight of the added electric
propulsion system, yet still gives us plenty of range (about 360 miles
motoring between the diesel engines and electric pods, more if we are
willing to slow down). On short passage days, this is more than
sufficient since we will likely be sailing most of it anyway. 90%
of our planned passages are less than that distance so why not save the
weight?
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